1. Field of the Invention
The present invention relates to mobile stations, and more particularly, to an apparatus and method for ring tone output.
2. Description of the Related Art
“Cell” is the basic geographic unit of a wireless telephony system. A city or county is divided into smaller cells, each of which is equipped with a low-power radio transmitter/receiver (e.g., a base station system). The cells can vary in size depending on terrain, capacity demands, or other conditions. By controlling the transmission power, the radio frequencies assigned to one cell can be limited to the boundaries of that cell. The base station system comprises a base transceiver station (BTS) and a base station controller (BSC). The BTS handles the radio interface to the mobile station with the radio equipment, such as transceivers and antennas. The BSC provides the control functions, such as handoff, cell configuration data and control of radio frequency (RF) power levels in the BTS, and physical links between a message switching center (MSC) and BTS.
Two types of logical channels, such as a control channel (CCH) and a traffic channel (TCH), have been developed in accordance with telephony communication standards. CCHs are employed for various control signals, such as registration, authentication, call set-up, and the like. Traffic channels are defined in GSM using a 26 multi-frame, or a group of 26 time-division multiple access (TDMA) frames. With 26 frames, 24 are used for traffic channels, 1 is used for a control channel, and the remaining channel is unused.
In order to notify a user an incoming call, mobile stations, such as cellular phones, output audio signals, such as polyphonic ring tones or a harmonic ring tones. Conventionally, all ring tones are stored in a memory device of a mobile station, and output using a melody IC. The melody IC acquires a specific ring tone from the memory device according to configured settings and transmits it to a buzzer or a ringing speaker after receiving an incoming call signal via a control channel. It is noted that all the traffic channels are idle at that time.
Although the conventional mobile station provides adequate ring tone output, a melody IC and additional memory space are required to store and output various ring tones, resulting in extra hardware cost. In view of these limitations, a need exists for an apparatus and method for ring tone output, with reduced hardware cost.